Desensitized coated cyclonite and process of preparation



nited rates This invention relates to new desensitized explosives and to a method for their production.

Heretofore the usefulness of the high explosive cyclonite (RDX) has been severely restricted by its extremely low impact stability which renders the composition extremely unstable and highly dangerous for shipping and handling purposes. To overcome this difiiculty cyclonite in the past has been coated with inert waxes or resins which although reducing the sensitivity of the composition, at the same time severely reduced the overall explosive power of the substance.

We have now found that cyclonite may be desensitized to within safe limits without appreciable reduction of its explosive power by providing a coating of polymeric esters or a mixture of esters having the general formula:

EOE! en? ll II x wherein R is a hydrogen or alkyl radical, A is an alkylene radical containing from 1 to 2 carbon atoms inclusive, R is an alkyl radical, R is a hydrogen or nitro radical, and x, y and n are whole numbers.

These polymers are conveniently prepared by the heat polymerization of unsaturated esters as disclosed in assignees copending application No. 397,007, filed December 8, 1953.

Coating of cyclonite with such polynitro-containing esters has been found to efiectively increase the impact stability of cyclonite from at least 1/3 to in some cases more than threefold. At the same time, these coatings possess a suificient oxygen content of their own so as to contribute rather than detract from the total explosive power of the coated composition. To illustrate the effect of such coatings upon the explosive power and impact stability of cyclonite as compared to the uncoated or beeswax or resin coated cyclonite, a series of these compositions were prepared and tested. The results of these tests are listed in the table set forth below:

TABLE [Properties of desensitized cyclonite] 1 This calculation is based on the inclusion of from 1 to 2.5% of a wetting agent.

atent Patented Sept. 19, 1961 The impact stability was determined with a 2 kg. weight by standard testing procedures.

The oxygen balances of these compositions are used to measure their explosive power. Oxygen balance is defined herein as the amount of additional oxygen, expressed as weight percent, necessary to convert all of the carbon present in the composition to carbon dioxide and all the hydrogen present to water.

It is apparent from the table above that the oxygen deficiencies of the compositions prepared in accordance with this invention are substantially lower than those exhibited by the wax coated cyclonite and in some cases approach that of the uncoated cyclonite. Moreover, it is also seen that the desired degree of high impact stability is also obtained by this means.

Both the mono and dinitro polyester used in the practice of this invention are excellent desensitizing agents,

however, certain of their properties differ and hence, one

may be preferred to the other in certain instances. It has been found that greater flexibility, resilience, and castability are provided by the polymers of the mono-nitro esters; however, the polymers of the dinitro esters have a higher oxygen content, thus it is sometimes desirable to use a mixture of the mono and dinitro esters as the coating material. Such a mixture possesses a blend of these properties and may be varied in proportion so as to enhance certain properties thereby providing materials having specialized physical and explosive characteristics.

The coatings of this invention are ordinarily applied by precipitating the coating material from a dispersion or suspension directly onto the explosive. Ordinarily the solubility characteristics of the ester employed determine the type of dispersion used. If it is found that the polymer is not soluble in a convenient re-agent, it is usually desirable to precipitate it directly from the polymerization mixture onto the explosive. However, whenever the commercial solvent for the polymer is available it isv usually more convenient to apply the coating to the explosive from solution followed by the subsequent removal of the solvent.

Since it is usually desirable to obtain an evenly distributed uniform coating on the explosive it is usually necessary to conduct the coating process in the presence of a wetting agent. This has been found to substantially.

improve the texture and uniformity of the coating. The wetting agent is usually provided in quantities of from about 2.5% to 10% by weight. Amounts less than about 2.5 do not produce satisfactory results. It has been found.

that amounts in excess of 2.5% may be used, however, this was not found to appreciably enhance the physical properties of the polymer thus the preferred amount is about 2.5% since this provides the optimum in physical ordinarily the preferred agent due to its greater commer cial availability.

It has also been found that best results are obtained when the coating comprises from about 5.0% to 12.0% of the explosive composition. The use of amounts less'than',

about 5% do not suificiently lower the sensitivity of the explosive while amounts in excess of about 12.0% do not add to the desensitization but merely decrease the ex plosive power. Optimum results were obtained when the coating accounted for about 10.0% of the explosive composition.

The following examples are provided to more clearly illustrate our invention. It is to be understood, however, that these examples are presented merely as a means of illustration and are not intended to limit thescope of the invention in any way.

3 EXAMPLE 1 Coating cyclonite with 2,2-dinitro-1-butyl acrylate polymer from suspension In a container fitted with a mechanical stirrer, was placed 100 ml. of water, a suspension containing 1.0 gm. of poly-2,2-dinitrobutyl acrylate, 0.2 gm. of sorbitan trioleate, and 20.0 gm. cyclonite. The reaction mixture was stirred for ten minutes and filtered. The coated explosive was washed with water and dried. The coating constituted 10% by weight of the composition and the impact stability of the composition was 85 cm./2 kg.

EXAMPLE II Coating cyclonite with 2,2-dinitr-1-butyl acr yl'ate polymer from emulsion in methanol medium Twenty ml. of methanol were placed in a reactor equipped with a mechanical stirrer. Stirring was started slowly and one gm. of the cylonite was added followed by 0.49 gm. sorbitan trioleate. The polymerization mixture containing poly-2,2-dinitro-l-butyl acrylate was then added dropwise to the suspension. The reaction mixture was stirred as rapidly as possible for one minute, the cyclonite was separated by filtration, washed with methanol, and dried in vacuo. The coating constituted 10% by weight of the composition and the impact stability of the composition was greater than 100 cm./ 2 kg.

EXAMPLE IH Coating cylonite with 2,2-dinitro-1-butyl acrylate polymer from emulsion in aqueous medium Three ml. of water was placed in a reactor fitted with a mechanical stirrer. Stirring was started and sorbitan trioleate was added dropwise. The polymerization emulsion was added dropwise and 1.0 gm. cyclonite was poured into the mixture which was then rapidly stirred for minutes. Three ml. methanol was added and stirring was continued for 2 minutes. The sample was collected, washed with methanol and dried. The impact stability of the composition was greater than 100 cm./2 kg.

EXAMPLE IV Coating cylonite with 2,2-a'initro-1-propyl acrylate polymer from emulsion A polymerization mixture containing 2 gm. 2,2-dinitrol-propyl acrylate was added dropwise to a mixture of water. Cyclonite was poured into the mixture which was then rapidly stirred. Sodium chloride was added and stirring was continued. The sample was collected, washed and dried. The coating comprised 5% by weight of the composition and the impact stability of the composition was 40 cm./2 kg.

EXAMPLE V Coating cylonite with 2,2-dinitro-I-butyl methacrylate polymer from emulsion 2,2-dinitro-1-butyl methacrylate was deposited on cyclonite from a polymerization mixture by the addition of sodium chloride as described in Example IV. The coati-ng comprised 12% by weight of the composition and the impact stability of the composition was 68 cm./ 2 kg.

EXAMPLE VI Coating cyclonite with 2,2-dinitro-1-butyl acrylate polymer from solution To a reactor fitted with a mechanical stirrer, thermometer and dropping funnel was added 50 ml. water which was heated to a temperature of 85 C. Sorbitan trioleate was added and stirred for 2 minutes; 20 gm. cyclonite was added and stirred 5 minutes. The 2-nitro-l-butyl acrylate polymer, dissolved in 15 ml. methyl isobutyl ketone, was added dropwise to the solution. When the addition of the polymer was completed, the solvent was azeotropically distilled and the coated cyclonite filtered, washed with water and dried. The coating comprised 5% by weight of the composition and impact stabihty of the composition was greater than 100 cm./2 kg.

EXAMPLE VII Coating cyclonite with copolymers of 10% 2-nitr '.0.-1 butyl acrylate and 2,2-dinitr0-1-butyl acrylate from solution Cyclonite was coated with the copolymer dissolved in methyl isobutyl ketone by following the procedure described in Example VI, to produce a composition having an impact stability of greater than cm./ 2 kg. The coating constituted 10% by weight of the composition.

EXAMPLE VIII Coating cyclonite with copolymers of 20% Z-nitro-I-butyl acrylate and 80% 2,2-dinitr0-1-butyl acrylate from solution Cyclonite was coated with the copolymer dissolved in methyl isobutyl ketone by following the procedure described in Example VI to produce a composition having an impact stability of greater than 100 cm./2 kg. The coating constituted 10% by weight of the composition.

It is apparent from the above discussion that we have succeeded in preparing explosive compositions having a combination of properties, namely high impact stability and explosive power, which heretofore have been mutually exclusive. Our invention provides explosive compositions which are safer, easier to handle and to transport than known compositions of comparable explosive strength. Our compositions find valuable use in many known capacities such as rocket and jet propellants and also may be useful for many purposes heretofore unfulfilled due to lack of an impact stable, high explosive.

We claim:

1. As compositions of matter, cyclonite coated with a desensitizing resin prepared by condensing a composition selected from the group consisting of monomers having the structural formula:

and mixtures of said monomers with monomers having the structural formula:

R 0 NO: CH2=(I JJO?A(|'JH,R wherein A is an alkylene radical having from 1 to 2 carbon atoms, R is a radical selected from the group consisting of hydrogen and lower alkyl radicals, and R is a lower alkyl radical.

2. The composition of claim 1 wherein the said desensitizing resin comprises from about 5 to about 12% by weight of the total explosive composition.

3. As a composition of matter, cyclonite coated with a desensitizing resin prepared by polymerization of a composition having the structural formula:

wherein A is a lower alkylene radical, having from 1 to 2 carbon atoms, R is a radical selected from the group consisting of hydrogen and lower alkyl radicals, and R is a lower alkyl radical.

4. As a composition of matter, cyclonite coated with a desensitizing resin prepared by polymerizing 2,2-dinitrobutyl acrylate.

5. As a composition of matter, cyclonite coated with a desensitizing resin prepared by polymerizing 2,2-dinitrobutyl methacrylate.

6. As a composition of matter, cyclonite coated with a desensitizing resin prepared by polymerizing 2,2-dinitropropyl acrylate. V l

7. As a composition of matter, cyclonite coated with a desensitizing resin prepared by polymerizing a mixture of 2,2-dinitrobutyl acrylate and 2-nitrobutyl acrylate.

8. The method of preparing a desensitized cyclonite composition which comprises precipitating a desensitizing resin prepared by polymerizing a composition selected from the group consisting of polynitro monomers having the structural formula:

and mixtures of said polynitro monomers with mononitro monomers having the structural formula:

wherein A is an alkylene radical, having from 1 to 2 carbon atoms, R is a radical selected from the group consisting of hydrogen and lower alkyl radicals, and R is a lower alkyl radical, onto cyclonite from a suspension of said desensitizing resin.

9. The method of preparing a desensitized cyclonite composition which comprises coating cyclonite With a desensitizing resin prepared by polymerizing 2,2-dinitrobutyl acrylate, by precipitating said resin from dispersion onto said cyclonite.

10. The method of preparing a desensitized cyclonite composition which comprises coating cyclonite with a desensitizing resin prepared by polymerizing 2,2-dinitrobutyl methacrylate, by precipitating said resin from dispersion onto said cyclonite.

11. The method of preparing a desensitized cyclonite composition which comprises coating cyclonite with a desensitizing resin prepared by polymerizing 2,2-dinitropropyl acrylate, by precipitating said resin from dispersion onto said cyclonite.

12. The method of preparing a desensitized cyclonite composition which comprises coating cyclonite with a desensitizing resin prepared by polymerizing Z-nitrobutyl acrylate, by precipitating said resin from dispersion onto said cyclonite.

13. The method for preparing a desensitized cyclonite composition which comprises coating the cyclonite with a polymeric resin obtained by condensing Z-nitro-l-butyl acrylate with 2,2-dinitro-1-butyl acrylate by precipitating said resin from a suspension onto cyclonite.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,169 Agre et al. June 12, 1945 2,404,688 Bruson et a1 July 23, 1946 2,710,830 Roy et a1. June 14, 1955 FOREIGN PATENTS 574,271 Great Britain Dec. 31, 1945 655,585 Great Britain July 25, 1951 

1. AS COMPOSITION OF MATTER, CYCLONITE COATED WITH A DESENSITIZING RESIN PREPARED BY CONDENSING A COMPOSITION SELECTED FROM THE GROUP CONSISTING OF MONOMERS HAVING THE STRUCTURAL FORMULA: 